It is proposed that, in a printed wiring board, an insulator board includes a plurality of conductor patterns and the conductor patterns are interconnected by a conductive compound in a via-hole formed in the insulator board. As a manufacturing method for such a printed wiring board, a method shown in FIG. 12A is proposed. In this method, a substantially cylindrical via-hole 124 is formed in an insulator board 123, which is made of prepreg in B stage status prepared by impregnating a core material such as glass cloth with unset thermosetting resin. A conductive paste 150, which is an interlayer connecting material consisting of metal particles and binder resin made of unset thermosetting resin, is packed in the via-hole 124. Subsequently, the board and conductive foils 122 forming a conductor pattern are laminated.
By hot-pressing this piled body, as shown in FIG. 12B, the conductive paste 150 becomes a unified conductive compound 151 with the setting of the binder resin, and conductive foils 122 forming conductor patterns are interconnected by the substantially cylindrical conductive compound 151 formed in the substantially cylindrical via-hole 124.
In this proposed art, interconnection between the conductive foils 122 forming conductor patterns is achieved with the substantially cylindrical conductive compound 151. Therefore, in a case that the printed wiring board incurs a stress due to deformation such as bending, the conductive compound 151 is likely to incur stress concentration in the vicinity of a junction part 151b that is a junction part with the conductor pattern (the conductive foil 122). If repeated or large stress concentration is generated in the vicinity of the junction part 151b, reliability of the interconnection is lowered.